untar.js

/* globals Blob: false, Promise: false, console: false, Worker: false, ProgressivePromise: false */

const basePath = import.meta.url.replace(/[^\/]*$/, '');
var workerScriptUri = basePath + 'untar-worker.js'; // Included at compile time

var global = window || this;

var URL = global.URL || global.webkitURL;

/**
Returns a ProgressivePromise.
*/
function untar(arrayBuffer) {
	if (!(arrayBuffer instanceof ArrayBuffer)) {
		throw new TypeError("arrayBuffer is not an instance of ArrayBuffer.");
	}

	if (!global.Worker) {
		throw new Error("Worker implementation is not available in this environment.");
	}

	return new ProgressivePromise(async function(resolve, reject, progress) {
		const _readBlob = async (src, text) => {
			const res = await fetch(src);
	  	return await res.blob();
		};
		var worker = new Worker(URL.createObjectURL(await _readBlob(workerScriptUri)));

		var files = [];

		worker.onerror = function(err) {
			reject(err);
		};

		worker.onmessage = function(message) {
			message = message.data;

			switch (message.type) {
				case "log":
					console[message.data.level]("Worker: " + message.data.msg);
					break;
				case "extract":
					var file = decorateExtractedFile(message.data);
					files.push(file);
					progress(file);
					break;
				case "complete":
					worker.terminate();
					resolve(files);
					break;
				case "error":
					//console.log("error message");
					worker.terminate();
					reject(new Error(message.data.message));
					break;
				default:
					worker.terminate();
					reject(new Error("Unknown message from worker: " + message.type));
					break;
			}
		};

		//console.info("Sending arraybuffer to worker for extraction.");
		worker.postMessage({ type: "extract", buffer: arrayBuffer }, [arrayBuffer]);
	});
}
window.untar = untar;

var decoratedFileProps = {
	blob: {
		get: function() {
			return this._blob || (this._blob = new Blob([this.buffer]));
		}
	},
	getBlobUrl: {
		value: function() {
			return this._blobUrl || (this._blobUrl = URL.createObjectURL(this.blob));
		}
	},
	readAsString: {
		value: function() {
			var buffer = this.buffer;
			var charCount = buffer.byteLength;
			var charSize = 1;
			var byteCount = charCount * charSize;
			var bufferView = new DataView(buffer);

			var charCodes = [];

			for (var i = 0; i < charCount; ++i) {
				var charCode = bufferView.getUint8(i * charSize, true);
				charCodes.push(charCode);
			}

			return (this._string = String.fromCharCode.apply(null, charCodes));
		}
	},
	readAsJSON: {
		value: function() {
			return JSON.parse(this.readAsString());
		}
	}
};

function decorateExtractedFile(file) {
	Object.defineProperties(file, decoratedFileProps);
	return file;
}